Effect of dry-heating on pasting properties of starch-gum hydrocolloid systems

The main aim of this thesis was to investigate the effects of gum addition (gum ghatti and carboxymethyl cellulose) and dry heating process on the pasting property, gelatinization, apparent viscosity, syneresis and retrogradation rate, and light transmittance of native corn starch paste. For this purpose, native corn starch with and without gum, dry heated corn starch with and without gum, waxy corn starch with and without gum and dry heated waxy corn starch samples with and without gum were compared in terms of these properties. Generally gum ghatti was found more effective than CMC in terms of all properties except light transmittance of waxy corn starch samples. Dry heating process led to increase light transmittance of native starch while both dry heating and gum addition caused to decrease it. Gum addition and dry heating applications increased viscosity of native corn starch. The highest viscosity was observed in dry heated waxy starch samples with gum addition. As a result of the FT-IR spectroscopy, significant peaks were determined at around 3275 cm-1, 2130 cm-1, 1634 cm-1, 1150 cm-1, 1077 cm-1 and 1014 cm-1 wave number. It was also determined that both gum addition and dry heating reduced syneresis amount further. The least syneresis amounts had seen at waxy starch samples. Accumulations depending on gum using and more deformed and ruptured granules depending on heat treatment were observed by Polarized light microscope analysis. It was concluded that gum ghatti addition and dry heating application may be advisable for modification of native corn starch. Key Words: Corn starch, dry heating, gum ghatti, CMC